FOSSIL SEA-MATS. 



213 



of the lowest of the Vertebrates the order of fishes 

 represented by the Lancelet (Amphioxus lanceolatus) 

 that we may regard them as a bridge connect- 

 ing the Invertebrate and Vertebrate divisions of the 



Fig. i6q. Common Sea- Mat (F lustra truncate!), natural size, recent. 



animal kingdom. Indeed, the larvae of the Ascidians 

 are so much more highly organized than the adults 

 that Professor Ray Lankester and others regard the 

 Ascidia as degraded Vertebrates ! The geologist 



